Such devices include a rolling bearing one of the races of which turns and the other of which is fixed, the turning race being provided with a radial attack surface intended to come into contact with the end of a maneuvering member such as a diaphragm of the clutch, for example.
A non-turning maneuvering element supports the rolling bearing and, when acted on by a (mechanical, electrical or hydraulic) control member, moves the bearing axially to cause the attack surface of the turning race to press against the diaphragm of the clutch and actuate the clutch mechanism.
A self-centering or self-aligning sleeve is generally disposed between the inner race of the rolling bearing and the maneuvering element, said sleeve providing the axial connection between these two parts at the same time as, by virtue of its elasticity, allowing relative radial movement between them. The rolling bearing can therefore move in order to obtain radial alignment of the rotation axes of the bearing and the diaphragm so as to be self-centered on the latter. For more details of such a rolling bearing, see for example patent application FR-A1-2 883 347.
In the rolling bearing described in that document, there is provided a fixed seal on the outer race including a friction lip that rubs against a radial collar on the inner race.
Under some operating conditions, the seal of such a bearing can prove insufficient.